sunflowers have an internal clock


Sunflowers track the sun from east through west. Researchers thought they were just following the light of the sun, but experiments show that sunflowers still bend east to west when under a constant light source. From Scientific American:

It is one of the great symbols of summer: a sunflower (Helianthus annuus) bending to track the path of the Sun from east to west, straining to make the most of each day. At night, the sunflower eases back towards the east in preparation for daybreak.

Yet these flowers are not responding simply to light, but also to an internal clock, researchers have found.

Plant biologists Hagop Atamian and Stacey Harmer of the University of California in Davis grew sunflowers in a field and then transferred them to growth chambers with a fixed overhead light that was always on. The plants continued their daily journey from east to west and back for several days after the transfer, suggesting that they were not responding only to the direction of the light, but their own timekeeper.

“It brings into question whether there’s some sort of memory that’s found within the plant that allows this regulation,” says Mark Belmonte, a plant biologist at the University of Mannitoba in Winnipeg, Canada, who was not involved with the study. ”This could be a very fine-tuned process.”

Make sure you see them in action in the video.

truvia is toxic to fruit flies

Dead fruit fly. Picture from wikipedia

C&EN describes how a sixth grade science project lead to the discovery that Truvia, a sweetner from the stevia plant, is toxic to fruit flies:

The discovery wouldn’t have been possible without Simon D. Kaschock-Marenda, who went to his dad three years ago to pitch an idea. Knowing that his father was a neurobiologist at Drexel with access to a supply of fruit flies, the sixth-grader proposed a science fair project: He wanted to feed a variety of sugars and sweeteners to flies and see how the insects fared.

One of the sweeteners father and son purchased from the supermarket for testing was Truvia, made by Minneapolis-basedCargill. The pair mixed that sweetener and a number of others with Drosophila food, put each in a container with adult fruit flies, and waited.

Almost a week later, Marenda’s son pointed out that the flies in the Truvia container had died, while the ones feeding off the other sweeteners were still alive. Thinking the result might be a fluke, the youngster and his father repeated the experiment, only to obtain the same result. Flies raised on the Truvia-laced food survived for about six days, and flies fed table sugar lived around 40 to 50 days.

The research was moved into the father’s lab where he discovered that erythritol is responsible for toxicity:

[F]ruit flies given food laced with Pure Via, another sweetener derived from the stevia plant, didn’t react as they had to Truvia. Their life span was unaltered.

So O’Donnell sent Truvia off to be analyzed with high-performance liquid chromatography and got interesting results. “More than 90% of the Truvia was erythritol,” Marenda says.

[...]

To determine whether erythritol was indeed their culprit, Marenda, O’Donnell, and their team placed fruit flies in containers with increasing doses of erythritol. At the highest concentration the researchers tested—2 M erythritol—all the flies died after a day or two of feeding.

child actually not HIV free

HIV medications

A child thought to be cured of HIV is actually still infected. The child received aggressive treatment immediately after birth, which made the virus undetectable. Now the child is showing signs of viral infection again, after two years without therapy. From the Bloomberg:

The child, born to an HIV-infected mother, is now nearly four years old. It was found to have detectable HIV levels in its blood during a routine clinical care visit earlier this month, according to a statement by the National Institute of Allergy and Infectious Diseases.

Doctors had unintentionally stopped giving anti-retroviral treatments to the child at 18 months. When care resumed five months later, medical staff couldn’t detect the virus and the speculation was that the child was free of the illness.

“Obviously, as an individual patient it’s disappointing,” said Anthony Fauci, director of NIAID, in a telephone interview. “But we’re learning very important things. Our capability of detection isn’t good enough. This reservoir is extraordinary, and we need to get better tools to measure it accurately.”


drug delivery via red blood cells

A group of researchers have developed a method for attaching drugs to the surfaces of red blood cells. RBC precursor cells are engineered to express a surface protein (purple oval) with a sortase substrate sequence. When the precursor cells become RBCs, sortase is added to form an RBC-enzyme intermediate. A modified drug can then react with the intermediate to form an RBC-drug conjugate. Picture from cen.acs.org

In this week’s CEN, Stu Borman describes a new drug delivery strategy. Researchers at The Whitehead Institute have developed a method for conjugating drugs to red blood cell surfaces increase drug longevity and bioavailability:

 Hidde L. PloeghHarvey F. Lodish, and coworkers at MIT’s Whitehead Institute for Biomedical Research have created RBC-drug conjugates that could take drug longevity to another level (Proc. Natl. Acad. Sci. USA 2014, DOI: 10.1073/pnas.1409861111). They’ve shown longevities of 28 days in mice but hope for more in people, where RBCs live up to four months.

They engineer mouse or human RBC precursor cells to express a surface protein bearing a sequence recognized by the enzyme sortase. Once the cells develop into RBCs, they add sortase, forming a covalent RBC-enzyme intermediate. A modified drug can then react with the intermediate, expelling sortase and yielding an RBC-drug conjugate. Sortase-based cell-surface labeling is an established technique, but this is the first time it’s been used for diagnostic or therapeutic purposes.

is fracking causing an increase in earthquakes?

An oil rig.

Eric Hand reports on a new study in Science Magazine that attempts to correlate an increase in seismic activity in Oklahoma to the hydraulic fracturing boom there. Oklahoma has had more magnitude 3 earthquakes this year than California. In the process of extracting natural gas, large amounts of water are pumped or stored underground. The pressure that is built up is thought to weaken the forces keeping a fault locked, and potentially trigger a rupture. The study by Katie Keranen suggest that the pressure build up could trigger seismic activity as far as 35 km away, and could one day threaten Oklahoma City:

The vast majority of Oklahoma’s more than 9000 injection wells cause no trouble whatsoever. Not so with four high-volume disposal wells used in a dewatering operation near Oklahoma City, the study suggests. The wells pump more than 4 million barrels (477,000 cubic meters) of water into the ground every month. Katie Keranen, a geophysicist at Cornell University, and colleagues found that the four wells are capable of triggering the earthquakes. By combining precise maps of Jones swarm earthquakes with a hydrogeologic model, they showed that an expanding underground wave of pressure from the wells (named Chambers, Flower Power, Deep Throat, and Sweetheart) closely matched the places and times of the quakes in the swarm. The company that owns the wells, New Dominion, based in Tulsa, Oklahoma, declined to answer questions about the study and released a statement saying that it was based on “false assumptions.”

Keranen is concerned that the four disposal wells lie close to the Nemaha fault, which runs through Oklahoma City and is large enough to host a devastating magnitude-7 earthquake. The main fault is unlikely to rupture because local stresses push its two sides together, Keranen says, but an unmapped offshoot might be more susceptible to rising water pressures. In the long term, a magnitude-6 earthquake near Oklahoma City is a plausible hazard, she says.